The present invention is directed to a surface mount semiconductor device and, more particularly, to a surface mount device with a solder ball reinforcement frame.
Semiconductor device packaging fulfils basic functions such as providing electrical connections and protecting the die against mechanical and environmental stresses. Semiconductor devices are commonly packaged for surface mounting by embedding one or more semiconductor dies in an encapsulation material. Electrical contacts for connection with external circuits are exposed in an active face of the package and are connected internally with electrical contact pads on the semiconductor die. Various techniques are available for connecting the exposed electrical contacts of the package with external circuits.
FIG. 1 shows a conventional controlled collapse chip carrier connection (C5) semiconductor device 100. The semiconductor device 100 comprises one or more singulated semiconductor dies 102 embedded in a molding compound 104 and having electrical contact solder elements such as 106 of a ball grid array (BGA) on an active face of the die 102. The semiconductor die 102 is mounted on a laminated substrate 108 that has electrically conductive layers and vias separated by insulating layers, and back face electrical contacts 110 formed on the back face of the substrate 108 to provide interconnections between the BGA of the semiconductor die 102 and an array of active face internal electrical contact pads 112 on the active face 114 of the substrate 108. A further array of electrical contact solder elements 116 form an external BGA on the active face 114 of the device 100. Patterning of the electrically conductive layers and vias in the substrate 108 enables the array of pads 106 on the semiconductor die 102 to be redistributed geometrically, so that the BGAs 112, 116 on the active face 114 of the device 100 may have a different geometry from the BGA on the active face of the semiconductor die 102. A solder mask 118 is formed on the active face 114 of the device. The solder mask 118 is applied to the substrate 108 by silk-screening or spraying a thin layer of lacquer or other polymer to protect the electrical contact pads 112 from oxidation and to prevent solder bridges from forming between closely spaced solder pads. Openings are etched in the solder mask 118 for the individual external electrical contact solder elements 116 to contact the electrical contact pads 112. The electrical contact elements 116 of the external BGA are placed on the contact pads 112 on the active face 114 of the substrate 108 and are held in place with a sticky flux until in use the assembly is heated in order to solder the device 100 to an external PCB (not shown).
When fabrication of the semiconductor device 100 is complete, it is delivered to the next phase of integration in a system, typically to a customer. During handling of the completed device 100, there is a risk of damage to the external BGA. Individual electrical contact elements 116, especially in the periphery close to the edges of the device 100 may be damaged or knocked away. The solder mask 118 provides no significant protection to the BGA, because it is thin and its material is not robust.
Therefore, it is desirable to reinforce the mechanical connections and increase the reliability of the electrical connections established by the external electrical contacts in use when the device is mounted on the external support.